Investigation of mandibular trabecular bone in patients with drug-related osteonecrosis of the jaw using fractal analysis method

Bisphosphonates are important drugs used in many medical fields, especially in oncology. They are prescribed for their antiresorptive or antitumor potential in multiple therapy in patients with multiple myeloma, metastatic cancer and osteoporosis. The term bisphosphonate-associated osteonecrosis of the jaw was first coined by Robert E. Marx in 2003. In 2007, the Commission of the American Association of Oral and Maxillofacial Surgeons defined bisphosphonate-related osteonecrosis of the jaw (BRONJ) as a common complication after these treatments. This has been observed in patients taking bisphosphonates to treat malignant bone metastases and osteoporosis. In 2014, the American Association of Oral and Maxillofacial Surgeons Commission changed the term BRONJ to MedicationRelated Osteonecrosis of the Maxilla (MRONJ). This change was deemed necessary due to the identification of cases of osteonecrosis of the jaw associated with other antiresorptive (denosumab) and antiangiogenic therapy. A fractal is characterized as a complex set of structures that are self-similar and cannot be described by common geometric shapes such as square, circle, triangle. Increasing complexity in a structure leads to an increase in fractal dimension (FD). Structures with high FD are more complex, while structures with low FD show a simpler layout. Fractal dimension assessment on panoramic images can provide information about the early changes of MRONJ in the mandible. The aim of our study was to determine the early changes in the mandible, where MRONJ is more common, and in which regions of the mandible these changes can be seen earlier by fractal dimension analysis.In this retrospective study, 30 MRONJ patients with a mean age of 64.2 years and 30 age- and sex-matched control patients were included. Control patients had no systemic disorders. Panoramic images (OPG/Planmeca Promax, Helsinki, Finland) of the patients were selected, exported in TIFF format and saved in Image J software (National Institutes of Health, Bethesda, MD, USA). For standardization of the images, specific regions of interest (ROI) including trabecular bone were selected based on anatomical structure and fractal dimension (FD) analysis was performed in Image J software. FB analysis of each sample was performed using thebox counting method. Statistical Package for the Social Sciences (SPSS) 25.0 was used for statistical analysis of the data. The selected areas are as follows:ROI-1 In the center of the necrotic areaROI-1A. In intact bone symmetrical to the necrotic areaROI-2. At the geometric center of the area between the sigmoid notch and mandibular foramenROI-3. In the area anterior/mezial to the mental foramenROI-4. In the gonial region below the mandibular foramenROI-5. On the distal side of the second premolar, in the region above the mandibular canal.When the ROIs were averaged, it was found that patients with MRONJ had significantly lower ROI5 measurements than patients in the control group. No significant difference was observed in other ROI regions.In conclusion, it can be said that the use of FB analysis may be useful in detecting early changes of MRONJ. ROI 5 region can be suggested as a reference region that can be used in the evaluation.